In 2014, some news reports stating that children wearing ortho-k lenses had 5 times more risk of getting microbial keratitis. In this blog entry, I would like to discuss whether it is totally true or not.
The news reports are based on the results of the 2 research published by the Chinese University of Hong Kong. 1,2 After reading through them carefully, I could not find any concrete and conclusive evidence showing that children wearing ortho-k lenses had 5 times more risk of getting microbial keratitis. One of the research found that from 2001 to 2010, there are 15 patients with age 18 or below being admitted to the Prince of Wales Hospital in Hong Kong due to contact lens wear, seven of them are ortho-k lens wearers.2 Another one found that from 2003 to 2013, there are 121 patients with age 23 or below being admitted to the Hong Kong Eye Hospital due to contact lens wear, twenty-three of them are ortho-k lens wearers.1
Therefore, those findings can only conclude that wearing ortho-k lenses could lead to microbial keratitis. It still needs higher quality clinical trials to find out the incidence rate of microbial
keratitis due to ortho-k wear.
In 2013, there is a research from America attempting to estimate the incidence rate of microbial keratitis associated with ortho-k lens wear. They surveyed 200 optometrists who practised orthokeratology, and found that the estimated incidence rate of microbial keratitis was 14 in 10000 ortho-k wearing children per year.3
Such incidence rate is similar to adults who wore daily silicone hydrogel soft contact lenses (A research from Australia found that the incidence rate of microbial keratitis was 12 in 10000 silicone hydrogel soft contact lens wearing adults per year 4). Due to the difference in experimental design, direct comparison of the incidence rate from both studies is not applicable, however they still have some referencing value. With the consideration of the aforementioned figures, and the pros and cons of orthokeratology, parents can consider whether it is worthwhile to start orthokeratology for their kids.
As a matter of fact, wearing any kinds of contact lenses will increase the risk of getting microbial keratitis. If the wearers can follow strictly the instructions given by the optometrists, and had regular aftercare visits (3-4 monthly for ortho-k wearers), risk of having microbial keratitis and other contact lens related complications must be able to keep to a minimum.5
By Paco Chan, Registered (Part I) Optometrist
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